Dear forum members,
Let us consider the circuit of the picture which provides a 5volt power to a USB2 port in a laptop. the power line is called +USB_VCCA. U40 provides this power when the En pin is low. There are two capacitors C974 and C975 that hold +USB_VCCA.
I see a problem in this circuit: when power is disconnected from the laptop, +5VALW reaches 0v immediately, but +USB_VCCA stays high. it takes about 5 minutes for +USB_VCCA to reach gradually from 5v to 3v to 2v to 0v. no USB device was connected when I tested it.
Do you think that C974 and C975 are defective that hold the +USB_VCCA power for such a long time?
when I turn the laptop off, U40 turns off, but C974 and C975 apply a voltage to U40. Do you think this may damage U40?
thanks
Let us consider the circuit of the picture which provides a 5volt power to a USB2 port in a laptop. the power line is called +USB_VCCA. U40 provides this power when the En pin is low. There are two capacitors C974 and C975 that hold +USB_VCCA.
I see a problem in this circuit: when power is disconnected from the laptop, +5VALW reaches 0v immediately, but +USB_VCCA stays high. it takes about 5 minutes for +USB_VCCA to reach gradually from 5v to 3v to 2v to 0v. no USB device was connected when I tested it.
Do you think that C974 and C975 are defective that hold the +USB_VCCA power for such a long time?
when I turn the laptop off, U40 turns off, but C974 and C975 apply a voltage to U40. Do you think this may damage U40?
thanks
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